Zeolite compositions and preparation and use thereof

Abstract

This invention relates to novel compositions of zeolites or microporous metallosilicates characterized by a continuous spatial distribution of the metal and silicon in the crystals and characterized by a crystal surface enriched in silicon relative to the internal part of the same crystals. This invention also relates to a synthesis method of producing these metallosilicates with spatial distribution of the constituting elements. These novel zeolitic compositions can be used in various hydrocarbon conversion reactions. The crystalline metallosilicates can be selected from the group consisting of aluminosilicates, gallosilicates, ferrosilicates, titanosilicates and borosilicates.

1. A process for producing a crystalline metallosilicate composition, the process comprising the steps of:
 (a) providing a two-phase liquid medium comprising an aqueous liquid phase and a non-aqueous liquid phase, the two-phase liquid medium further comprising at least one silicon-containing compound and at least one metal-containing compound, wherein the at least one silicon-containing compound is present in both the aqueous liquid phase and the non-aqueous liquid phase, and the at least one metal-containing compound is present in substantially the aqueous liquid phase; and 
 (b) crystallising the crystalline metallosilicate composition from the two-phase liquid medium; wherein each crystallite has an outer surface and an inner part; and the metallosilicate composition has a continuous spatial distribution of silicon to metal, and an atomic ratio of silicon to metal that decreases continuously from the outer surface to the inner part of each crystallite. 
 
     
     
       2. A process according to  claim 1  wherein the at least one silicon-containing compound is selected from at least one of an alkali metal silicate, a tetraalkyl orthosilicate, precipitated silica, pyrogenic silica, and an aqueous colloidal suspension of silica. 
     
     
       3. A process according to  claim 1  wherein the at least one metal-containing compound is selected from at least one of the metal oxide, a metal salt, and a metal alkoxide. 
     
     
       4. A process according to  claim 3  wherein the metallosilicate is an aluminosilicate, and the at least one metal-containing compound comprises an aluminium compound for which the source of aluminum is selected from at least one of hydrated alumina dissolved in an alkaline solution, aluminum metal, a water-soluble aluminum salt, such as aluminum sulphate or aluminium chloride, sodium aluminate and an alkoxide, such as aluminum isopropoxide. 
     
     
       5. A process according to  claim 3  wherein the metallosilicate is a borosilicate, and the at least one metal-containing compound comprises a boron compound for which the source of boron is selected from at least one of hydrated boron oxide dissolved in an alkaline solution, a water-soluble boron salt, such as boron chloride, and an alkoxide. 
     
     
       6. A process according to  claim 3  wherein the metallosilicate is a ferrosilicate, and the at least one metal-containing compound comprises an iron compound for which the source of iron is a water soluble iron salt. 
     
     
       7. A process according to  claim 3  wherein the metallosilicate is a gallosilicate, and the at least one metal-containing compound comprises a gallium compound for which the source of gallium is a water soluble gallium salt. 
     
     
       8. A process according to  claim 3  wherein the metallosilicate is a titanosilicate, and the at least one metal-containing compound comprises a titanium compound for which the source of titanium is selected from at least one of titanium halides, titanium oxyhalides, titanium sulphates and titanium alkoxides. 
     
     
       9. A process according  claim 1  wherein the non-aqueous liquid phase comprises an organic solvent which is substantially water insoluble or water immiscible. 
     
     
       10. A process according to  claim 9  wherein the organic solvent comprises at least one of an alcohol having at least 5 carbon atoms or a mercaptan having at least 5 carbon atoms. 
     
     
       11. A process according to  claim 10  wherein the alcohol has up to 18 carbon atoms and the mercaptan has up to 18 carbon atoms. 
     
     
       12. A process according to  claim 1  wherein the weight ratio of the liquid medium of the non-aqueous liquid phase to the liquid medium of the aqueous liquid phase is from 0.01/1 to 5/1. 
     
     
       13. A process according to  claim 1  wherein the molar ratio of the liquid medium of the non-aqueous liquid phase to the silicon in the two-phase liquid medium is from 100/1 to 0.5/1. 
     
     
       14. A process according to  claim 1  further comprising the step of forming the two-phase liquid medium by providing a first, aqueous, medium and a second, non-aqueous, medium and combining the first and second media together to form the two-phase liquid medium. 
     
     
       15. A process according to  claim 14  wherein the first, aqueous, medium comprises a first portion of the at least one silicon-containing compound and the second, non-aqueous, medium comprises a second portion of the at least one silicon-containing compound. 
     
     
       16. A process according to  claim 15  wherein the first, aqueous, medium comprises from 25 to less than 100 wt % of the at least one silicon-containing compound and the second, non-aqueous, medium comprises from greater than 0 to 75 wt % of the at least one silicon-containing compound. 
     
     
       17. A process according to  claim 14  wherein the first, aqueous, medium comprises a first silicon-containing compound and the second, non-aqueous, medium comprises a second silicon-containing compound. 
     
     
       18. A process according to  claim 14  wherein the second silicon-containing compound comprises a silicon alkoxide. 
     
     
       19. A process according to  claim 14  further comprising adding to the two-phase liquid medium an aqueous solution or dispersion of the at least one metal-containing compound. 
     
     
       20. A hydrocarbon conversion process comprising:
 providing a crystalline metallosilicate composition produced in accordance with  claim 1  as a catalyst; and 
 contacting said catalyst with a hydrocarbon feed. 
 
     
     
       21. A crystalline metallosilicate composition comprising crystallites having a crystal outer surface layer having a depth of about 10 nm below the outer surface, and an inner part extending inwardly from a depth of about 50 nm below the outer surface, wherein the atomic ratio of silicon to metal in the metallosilicate composition is at least 1.5 times higher in the crystal outer surface layer as compared to that in the inner part, and wherein the metallosilicate composition has a continuous spatial distribution of silicon to metal, and an atomic ratio of silicon to metal that decreases continuously from the outer surface to the inner part of each crystallite. 
     
     
       22. A crystalline metallosilicate composition according to  claim 21  wherein the inner part has a silicon/metal atomic ratio of from 15 to 1000, and the crystal outer surface layer has a silicon/metal atomic ratio of from 22.5 to 15000. 
     
     
       23. A crystalline metallosilicate composition according to  claim 21  or  claim 22  wherein the inner part has a substantially constant silicon/metal atomic ratio. 
     
     
       24. A crystalline metallosilicate composition according to  claim 21  wherein in the inner part the silicon/metal atomic ratio in the walls, constituting the pores in the crystalline metallosilicate composition, is substantially the same as the average silicon/metal atomic ratio of the inner part. 
     
     
       25. A crystalline metallosilicate composition according to  claim 21  wherein the metallosilicate is an aluminosilicate, a borosilicate, a ferrosilicate, a gallosilicate, or a titanosilicate. 
     
     
       26. A process of hydrocarbon conversion comprising:
 providing a crystalline metallosilicate composition in accordance with  claim 21  as a catalyst; and 
 contacting said catalyst with a hydrocarbon feed. 
 
     
     
       27. A process for producing a crystalline metallosilicate composition, the process comprising the steps of:
 (a) providing an aqueous liquid comprising at least one silicon-containing compound dissolved or dispersed therein; 
 (b) providing a non-aqueous liquid; 
 (c) combining the aqueous liquid and the non-aqueous liquid to form a two-phase liquid medium; 
 (d) either (i) additionally providing the aqueous liquid provided in step (a) with at least one metal-containing compound dissolved or dispersed therein or (ii) adding, either to the aqueous liquid provided in step (a), prior to step (c), or to the two-phase liquid medium formed in step (c), an aqueous solution or dispersion of the at least one metal-containing compound, and 
 (e) crystallising the crystalline metallosilicate composition from the two-phase liquid medium; wherein each crystallite has an outer surface and an inner part; and wherein the metallosilicate composition has a continuous spatial distribution of silicon to metal, and an atomic ratio of silicon to metal that decreases continuously from the outer surface to the inner part of each crystallite. 
 
     
     
       28. A process according to  claim 27  wherein the at least one silicon-containing compound is selected from at least one of an alkali metal silicate, a tetraalkyl orthosilicate, precipitated silica, pyrogenic silica, and an aqueous colloidal suspension of silica. 
     
     
       29. A process according to  claim 27  or  28  wherein the at least one metal-containing compound is selected from at least one of the metal oxide, a water-soluble metal salt, and a metal alkoxide. 
     
     
       30. A process according to  claim 27  wherein the metallosilicate is an aluminosilicate, a borosilicate, a ferrosilicate, a gallosilicate, or a titanosilicate. 
     
     
       31. A process according to  claim 27  wherein the non-aqueous liquid-comprises an organic solvent which is substantially water insoluble or water immiscible. 
     
     
       32. A process according to  claim 31  wherein the organic solvent comprises at least one of an alcohol having at least 5 carbon atoms or a mercaptan having at least 5 carbon atoms. 
     
     
       33. A process according to  claim 32  wherein the alcohol has up to 18 carbon atoms and the mercaptan has up to 18 carbon atoms. 
     
     
       34. A process according to  claim 27  wherein the weight ratio of the non-aqueous liquid to water in the two-phase liquid medium is from 0.01/1 to 5/1. 
     
     
       35. A process according to  claim 27  wherein the molar ratio of the non-aqueous liquid phase to the silicon in the two-phase liquid medium is from 100/1 to 0.5/1. 
     
     
       36. A process according to  claim 27  wherein the aqueous liquid provided in step (a) comprises a first silicon-containing compound and the non-aqueous liquid provided in step (b) comprises a second silicon-containing compound dissolved or dispersed therein. 
     
     
       37. A process according to  claim 36  wherein in the two-phase liquid medium the first silicon-containing compound comprises from 25 to less than 100 wt % of the at least one silicon-containing compound and the second silicon-containing compound comprises from greater than 0 to 75 wt % of the at least one silicon-containing compound. 
     
     
       38. A process according to  claim 36  or  claim 37  wherein the second silicon-containing compound comprises a silicon alkoxide. 
     
     
       39. A process according to  claim 27  wherein the aqueous liquid provided in step (a) comprises all of the at least one silicon-containing compound. 
     
     
       40. A process according to  claim 27  wherein the aqueous solution or dispersion of the at least one metal-containing compound added in step (d) comprises all of the at least one metal-containing compound. 
     
     
       41. A process according to  claim 27  wherein the aqueous solution or dispersion of the at least one metal-containing compound added in step (d) further comprises a structure directing agent for the metallosilicate comprising at least one organic or inorganic compound containing nitrogen, oxygen, sulphur or phosphorous. 
     
     
       42. A process of hydrocarbon conversion comprising:
 providing a crystalline metallosilicate composition produced in accordance with  claim 27  as a catalyst; and 
 
       contacting said catalyst with a hydrocarbon feed.